Large caliber weapons deliver relatively large, heavy projectiles at relatively high velocities to distant targets. When the weapon is fired, a propellant burns and hot gasses rapidly expand in volume inside a gun barrel. The expanding gases accelerate a projectile along the length of the tubular barrel, ejecting the projectile at a high velocity from the muzzle end of the barrel. The expanding propellant gasses follow the projectile and are expelled into the atmosphere at velocities equaling or even exceeding those of the projectile, similar to an exhaust plume from a rocket. The combination of accelerating the projectile and the propellant gasses exiting the muzzle end of the gun barrel produces a large breach-directed recoil thrust (also called a recoil force or simply recoil) that is transmitted to the support structure.
Gun designers take these recoil forces into consideration during the design process, using physics principles related to conservation of momentum to predict the forces involved. Larger recoil forces generally require heavier and stronger gun components and support structures, both of which generally are more expensive. Smaller and lighter guns and support structures are not only less expensive, but they are easier to transport, which is another important consideration for gun designers.
Consequently, gun designers generally try to mitigate the recoil, and thus reduce the forces transmitted from the gun barrel to the support structure by installing or integrating a muzzle brake at or near the muzzle end of the gun barrel. A muzzle brake generally reduces the momentum of the recoiling components of a gun by diverting the flow of propellant gasses in a way that produces forces to counter the breach-directed recoil.
An early form of muzzle brake includes a series of holes drilled radially into the tubular gun barrel or an attachment to the barrel at the muzzle end. This design is sometimes referred to as a “pepper pot.” In other forms the muzzle brake may have a series of baffles perpendicular to the gun barrel axis or angled backward so that the outlet is closer to the breach end of the gun barrel than the inlet. The diverted high pressure gasses exert a force on the rearward-facing surfaces of the baffles that counteracts the recoil force created by the exhaust of the propellant gasses and the acceleration of the projectile.